Bald Neck in Week old chick

I have a gold laced Wyandotte chick with a bald spot on back of neck. I noticed it two days ago. The skin is raised and hard where it is bald. She is on pine shavings. Food and water readily available. Housed with nine other chicks. Temp is ninety. Red light only except when I am interacting with them. Help, please!

Today it seems the same. Not any worse. I caught her scratching at it though she can't reach it with her beak. I have both light and dark colored chicks and I haven't seen any mites or lice. Any suggestions on what it could be our treatment? Should I give it a few days? They are drinking water with electrolytes in them, should I use probiotics?